1. Field of the Invention
The present invention relates to a fusing apparatus and an image forming apparatus.
2. Description of Related Art
Conventionally, there is an image forming apparatus including a fusing apparatus which fuses an image (for example, toner image) formed on a recording medium (for example, sheet, etc.) to the recording medium. In the fusing apparatus, for example, a nipping section is formed by a belt and a roller in contact with each other, the belt supported by a plurality of rollers and the roller provided to face one of the rollers which supports the belt, and the nipping section nips a sheet and pressure is applied to the sheet. Heat is applied to the belt with a heater, etc., and the fusing apparatus applies pressure and heat simultaneously on the sheet nipped by the nipping section to fuse the image on the sheet.
In the fusing apparatus, fusing processing is performed on the sheet nipped by the nipping section while conveying the sheet with the rotating motion of the rollers and the sheet is ejected to a predetermined conveying path. Here, the ejected sheet may be attached to the outer peripheral surface of the belt which forms the nipping section. In this case, the sheet is not ejected to the predetermined conveying path (ejection failure). In an image of a sheet where such ejection failure occurs, the toner image is overheated, and therefore the image quality is poor, such as unevenness of the toner surface occurring. Moreover, with the sheet attached to the belt, the fusing apparatus cannot favorably perform the fusing processing afterward. Therefore, Japanese Patent Application Laid-Open Publication No. 2007-79411 describes an image forming apparatus which includes an injecting apparatus which injects a gas between the belt and the sheet passed and ejected from the nipping section in order to separate the sheet from the belt.
The pressure applied to the gas injected from the injecting apparatus decreases in the path from when the gas is injected to when the gas enters between the sheet and the belt. In order to favorably separate the sheet from the belt, it is preferable to inject a gas with high pressure between the sheet and the belt. Therefore, in order to keep the reduction of pressure of the injected gas to a minimum, it is preferable that the tip of the injecting opening (for example, nozzle shown in FIG. 10) of the injecting apparatus is close to the belt of the fusing apparatus as much as possible.
However, in a conventional image forming apparatus, when the tip of the nozzle is close to the belt of the fusing apparatus, the sheet may cause damage to the fusing apparatus.
Specifically, when the sheet which passes the nipping section and is ejected is not separated from the belt completely, the edge of the sheet may be caught on the tip of the nozzle. In this case, the sheet which is not separated completely is pushed in a narrow space between the tip of the nozzle and the belt when the belt is operated, and this causes jamming (sheet jamming). Here, the pushed and jammed sheet causes damage to the belt, etc. of the fusing apparatus. Damage to the fusing apparatus causes heavy damage such as cost for exchange of the fusing apparatus, decrease of productivity of the image forming apparatus not being able to perform image forming until the exchange is finished, and the like.
In the above description, an example where the sheet is attached to the belt is described, however, similarly, when the sheet is attached to the roller, the recording medium which is pushed in a narrow space between the tip of the nozzle and the roller and jammed damages the roller.